Internationally, the Institute has distinguished itself as the preeminent source of gemological knowledge and professionalism. The GIA Diamond Grading Reportand the GIA Diamond Dossier® are considered to be the world's premier credentials of diamond quality. Many retailers provide diamond certification, however no report is as unbiased and complete as a GIA diamond grading report. Diamonds of all shapes and sizes are sent to the Institute from every corner of the globe for diamond grading and analysis.

Some famous diamonds have been graded by GIA including the Hope Diamond (45.52 carats), the Steinmetz Pink (59.60 carats), the Taylor-Burton (69.42 carats), the Allnatt (101.29 carats), the De Beers Millennium Star (203.04 carats), the Centenary (273.85 carats), and the Incomparable (407.48 carats).

GIA is the creator of the revolutionary 4Cs of diamond value (carat, color, clarity, and cut). It is also the birthplace of the International Diamond Grading System™. Today, GIA’s D-Z color-grading scale, Flawless–I3 clarity-grading scale and Excellent-to-Poor cut-grading scale are recognized by virtually every professional jeweler and savvy diamond buyer in the world.